This invention relates to a swash-plate type compressor for compressing refrigerant gas circulating in an air conditioning system, and more particularly to improvements in or to the lubricant oil feeding arrangement of the swash-plate type compressor.
In a swash-plate type compressor of this kind in general, rotation of the swash plate which is obliquely secured on the drive shaft causes reciprocating motions of the pistons within their respective cylinder bores to carry out pumping actions in cooperation with suction valves and discharge valves. The swash plate and the pistons engage each other with balls and shoes intervening therebetween in a manner that rotation of the swash plate is transduced into reciprocating motions of the pistons. According to this arrangement, the swash plate, the shoes, the balls and the pistons have their sliding contact portions subjected to severe friction and therefore require to be permanently fed with lubricant oil. Conventional automatic lubricant oil feeding systems include an oil-splashing type in which an oil reservoir is provided below the swash plate and lubricant oil stored in the oil reservoir is splashed upwardly by the outer fringe of the rotating swash plate to be fed to the sliding contact portions of the aforementioned parts. Further, part of the lubricant oil thus splashed is transformed into an oily mist and guided together with the refrigerant gas floating in the swash plate chamber towards the low pressure chambers to lubricate the radial bearings journalling the drive shaft and their neighboring parts. The oily mist introduced into the low pressure chambers is mixed into the refrigerant gas in the same chambers and then discharged into the refrigerating circuit of the air conditioning system for circulation therein. The lubricant oil in the refrigerating circuit is again returned to the compressor and forced into the swash plate chamber together with blow-bye gas generated by the compression actions of the pistons and then again stored in the oil reservoir. Therefore, the amount of lubricant oil to be used in a compressor of this type is set at such a value as ensures that the lubricant oil always keeps a suitable surface level in the oil reservoir, taking into account the amount of lubricant oil to circulate in the refrigerating circuit.
However, if lubricant oil stagnates in a portion of the refrigerating circuit, there occurs a delay in the return of the lubricant oil to the oil reservoir, resulting in lowering of the oil surface level in the oil reservoir below the lower end of the outer fringe of the swash plate. This can cause the temporary phenomenon that no lubricant oil is splashed by the swash plate, leading to insufficient lubrication of the sliding contact portions of the swash plate, the shoes, etc., which may even involve seizure trouble.